The present invention relates to a friction clutch facing for use with a wet-type multi-plate clutch. Such multi-plate clutches generally comprise a plurality of interleaved clutch discs and clutch plates which engage to provide the transmission of energy from a drive engine to a drive wheel. Wet-type clutches also utilize a lubricant such as oil to reduce clutch wear, cool the friction facings of the clutch discs and provide desired hydrostatic forces between the clutch plates and clutch discs.
In the interest of optimizing clutch life, operational smoothness, and cooling efficiency for the friction facings, the literature and art relating to wet-type clutches evidences numerous clutch designs producing a large variety of friction facing materials and designs of friction facing materials. A common friction facing, currently available is typified by the disclosure of U.S. Pat. Nos. 4,260,047 and 4,674,616. Both patents disclose friction discs, for use with clutches, which are formed from friction material and produced from the joinder of a plurality of arcuate segments. Commonly, the arcuate segments are pre-grooved to allow for cooling oil to flow over the friction facing during clutch operation. Further, the arcuate segments are designed to interlock together to form an annular friction facing intended to be bonded to an annular core plate.
The creation and design of arcuate segment friction facings is intended to meet a goal of reducing the amount of waste produced during the manufacture of the friction facings. The friction facings are usually composed of sintered metal or paper which normally is impregnated with a phenolic resin. The friction facing segments are commonly cut from a continuous strip of rectangular sheeting composed of the friction material which is fed through the die or cutting apparatus. The friction material is relatively expensive and, therefore, it is desirable to optimize the elimination of waste from the manufacturing process. Further, elimination of waste product from the manufacture process assists in meeting compliance standards, for the proper disposal of any scrap, which are the focus of increasing regulation by current environmental regulations. Any scrap resulting from the cutting process must be disposed of in an appropriate manner and, because of the materials from which the friction facing is manufactured, this disposal is becoming increasingly costly. It is, therefore, a primary objective of the invention to effectively reduce the amount of scrap remaining after cutting of the friction facing segments. Of course, the most desirable objective for an improved method of manufacturing friction facing segments would be to produce a scrapless manufacturing process which uses nearly 100% of the available material, with little or no waste.
An ongoing objective for wet-type multiple clutch discs involves the provision of sufficient cooling and lubrication to the friction facings and clutch plates so that smooth engagement and disengagement of the clutch is maintained without creating excessive wear on the members of the clutch and friction facings. Many prior art friction facing designs incorporate the use of grooves or slot patterns within the facing material to achieve the desired cooling and lubrication by allowing the passage of a fluid such as oil through the friction facings. Such cooling grooves are generally produced from one of three methods. One method provides that the friction material is pre-grooved prior to being cut and applied to the clutch plate in a manner such as that taught by U.S. Pat. No. 4,260,047. Another method of producing grooves utilizes configured tooling to compress portions of the friction material during the hot pressure bonding process. The third and most preferred method involves producing cut grooves in a finished friction plate by mounting the plate into a fixture and passing a multiple gang of milling and grinding wheels through the friction material to cut distinct grooves of desired depth and definition.
It is an objective of the present invention to manufacture a friction clutch plate having distinct cooling groove patterns of desired depth and definition without the need for secondary operations and attendant machinery.
U.S. Pat. No. 5,094,331 discloses a variety of friction facing structures which are intended to distribute oil during operation of the clutch so as to remove frictional heat generated by the interaction of the friction facings and the clutch plates and also serve to absorb shocks produced when the clutch disc with friction facing and companion clutch plates are engaged and disengaged. The embodiments disclosed in the '331 patent provide for structures which have frictional surfaces spaced at predetermined intervals thereby creating oil passages having a width that becomes progressively smaller in a radial direction away from the center of the clutch disc to an outer circumferential edge of the clutch disc. These radial oil passages allow the oil to flow through the oil passages or grooves under centrifugal forces to cool the clutch discs and clutch plates even while the clutch discs and clutch plates are engaged. One embodiment described in the '331 patent provides for distinct oil passages and oil grooves being alternately defined in the frictional surface of the friction facing. The oil passages and oil grooves are constructed such that a large amount of oil will flow through the passages for a cooling effect and a large amount of oil will also be retained in the oil grooves. Consequently, the clutch discs can be cooled effectively and the clutch can also be smoothly engaged and disengaged since the oil retained in the oil grooves will exert a hydrostatic force to the clutch discs and the clutch plates as a result of the centrifugal forces acting on the clutch members. While friction facings of this design are effective in meeting their objectives, they are complex in design, often resulting in production difficulties due to the variety of grooves and passages provided within the facing material. The complexity of the designs of the '331 friction facing also leads to problems with scrap disposal. Therefore, it is desirable to improve upon the friction facings disclosed in the '331 patent by reducing the complexities of manufacture and continuing to strive toward the elimination of scrap.
Another embodiment of friction facings disclosed in the '331 patent discloses the use of a plurality of friction members attached to the opposing surfaces of the disc plate to define a plurality of oil passages extending radially outward from the inner peripheral edge to the outer peripheral edge of the clutch disc. Generally the oil passages have a width which becomes progressively smaller in the radially outward direction. Because the widths of the oil passages at the outer circumferential edges of the clutch discs have radially narrowed, the oil flowing into the passages tends to stay in the passages for a longer period of time, creating some hydrostatic pressure, dependent on the centrifugal force. Thus, the clutch discs are cooled and hydrostatic assistance is provided for separating the clutch discs and clutch plates away from each other. Other embodiments of friction facings in the '331 patent are shown of specific-type friction members. However, the common failing of all the designs of friction facings as shown in the '331 patent lies in their intricate shapes and designs which lead to manufacturing complexities, increased scrap production and the resultant concerns regarding proper disposal of the scrap. Further, the variety of facings disclosed in the '331 patent are all individually applicable to specific needs and types of applications for friction clutches and, generally speaking, cannot crossover in their intended uses. Therefore, it is an object of the invention to provide for friction facing segments which are nearly entirely scrapless in their manufacture.
It is another object of the invention to provide friction facing segments which are universally applicable to differing types of clutch usage.
It is yet another object of the present invention to provide friction facing segments which, depending upon their orientation when applied to the clutch disc or core, have divergent space between the segments.
Yet another object of the invention is to provide friction facing segments having structural advantages designated to produce or enhance oil flow through the spacing between the segments, such oil flow being dependent upon the direction of rotation of the disc.
Yet a further object of the invention is to produce a friction facing segment having a capability of maintaining static pressure and holding dynamic fluid flow within the spacing between the segments during operation of the engaged clutch disc and clutch plate.
Yet a further object of the invention is to provide for friction facing segments which, dependent upon their direction of rotation, will enhance the flow of oil into or the evacuation of oil from the friction facing.